Project Summary/Abstract Primary graft dysfunction (PGD) is the most common cause of morbidity and mortality after lung transplantation. Recent data indicate participation of a few specific pathways in acute lung injury models and post-transplant PGD. A better understanding of these specific pathways would offer mechanistic clues to PGD pathogenesis and potentially stimulate investigation of novel therapeutic avenues. In addition, identification of specific, individualized risk factors for PGD might allow future personalized therapy. Our preliminary data indicate that innate immune activation is important in PGD pathogenesis based on transcripts from donor lung tissue and in extracellular vesicles identified in perfusate from ex vivo lung perfusion failures (no transplant). Given these findings, there appears to be unmeasured injury to the lung despite normal physiologic measurements which needs to be further characterized. The long-term objective of our line of research is to understand the mechanism of PGD in human lung transplantation in order to identify strategies to identify donors at risk, prevent recipient death and expand the donor pool through better donor selection and use of ex vivo lung perfusion (EVLP) strategies. Our approach is to use gene expression in donor lung bronchoalveolar lavage to predict PGD and to examine the innate immunity pathways involved in PGD of transplanted donors and untransplantable donors placed on EVLP. The central hypotheses are that lung injury occurring in the donor lung prior to procurement can be evaluated by gene expression methods to determine PGD risk and understand common mechanisms of EVLP failure.